let app = document.getElementById('app')

let left = document.querySelector('.left')
let right = document.querySelector('.right')

left.addEventListener('mouseenter', () => {
    app.classList.add('left_hover')
})

left.addEventListener('mouseleave', () => {
    app.classList.remove('left_hover')
})

right.addEventListener('mouseenter', () => {
    app.classList.add('right_hover')
})

right.addEventListener('mouseleave', () => {
    app.classList.remove('right_hover')
})